I. Field of the Invention
The present invention relates to a document marking apparatus in which the documents, which may be cards, cheques, dockets, credit cards or similar items, are brought temporarily into contact with an impression stamp.
II. Description of the Prior Art
In marking apparatus produced hitherto, the impression stamp is attached either to a movable carrier which can be moved to apply the stamp to the document to be marked or else to a rotary impression roller which cooperates with a pressure roller, the document to be marked being, in this latter case, inserted between the two rollers, which are pressed one against the other, and the marking taking place when the stamp comes into contact with the document.
In such marking apparatus, inking is achieved either by using a porous rubber stamp impregnated with ink or by providing an inking pad to which the stamp is applied at the end of each marking operation. However, the use of an ink-impregnated stamp proves unsatisfactory in that, each time the stamp is pressed against a document, large amounts of ink tend to leave the stamp and be transferred to the document and there is a danger of this excess ink causing smudges which detract from the standard of the characters or symbols which are printed.
This disadvantage does not exist with marking apparatus which have a dry stamp and in which the stamp is inked by an inking pad. Marking apparatus of this type are known in which the stamp is attached to the end of a moving part and in which a mechanism is provided either to cause the stamp to be applied first to the inking pad and then to the document to be marked, or else to cause the inking pad to be moved aside at the moment when the stamp is moved to bring it into contact with the document. In general however, such arrangements are very complicated and cumbersome. Furthermore, delicate adjustments are necessary in their construction and they do not always operate satisfactorily owing, in particular, to loss of adjustment consequent to the rapid wear on the parts which make up the mechanism which operates the stamp or the inking pad.
In marking apparatus in which the stamp is attached to a rotary impression roller, this drawback has successfully been removed by providing, for the inking of the stamp, an inking roller which is applied against the impression roller each time the stamp passes in front of it. Nevertheless, such arrangements prove to be extremely complicated due to the fact that, to enable the stamp to be pressed against the document at a closely defined point, it is necessary to equip the arrangement with a suitable control system to co-ordinate the rotary movement of the impression roller and the advancing movement of the documents so that a document can only be inserted under the impression roller at the moment when the stamp has reached a predetermined position. Furthermore, such marking arrangements are totally unsuitable for marking documents which vary greatly in length from one document to another.